Author: edelsohn
Branch: ppc-jit-backend
Changeset: r56831:d1f2560c2012
Date: 2012-08-23 17:30 -0400
http://bitbucket.org/pypy/pypy/changeset/d1f2560c2012/
Log: Explain minimum ABI requirements for stack frame.
diff --git a/pypy/jit/backend/ppc/test/test_stackframe.py
b/pypy/jit/backend/ppc/test/test_stackframe.py
--- a/pypy/jit/backend/ppc/test/test_stackframe.py
+++ b/pypy/jit/backend/ppc/test/test_stackframe.py
@@ -45,4 +45,47 @@
SP -> --------------------------- --
+Minimum PPC64 ABI stack frame:
+
+
OLD FRAME
+ | BACK CHAIN |
+ - - - - - --------------------------- - - - - -- - - - - - - - - -
+ | | |
CURRENT FRAME
+ | PARAMETER SAVE AREA | |>> max_stack_params * WORD
+ | | |
+ --------------------------- --
+ (64 Bit) | TOC POINTER | WORD |
+ --------------------------- --
+ | | |
+ (64 Bit) | RESERVED FOR COMPILER | |>> 2 * WORD
+ | AND LINKER | |
+ --------------------------- --
+ | SAVED LR | WORD |
+ --------------------------- |>> 3 WORDS (64 Bit)
+ (64 Bit) | SAVED CR | WORD | 2 WORDS (32 Bit)
+ --------------------------- |
+ | BACK CHAIN | WORD |
+ SP -> --------------------------- --
+
+PARAM AREA = 8 doublewords = 64 bytes
+FIXED AREA = 6 doublewords = 48 bytes
+TOTAL = 14 doublewords = 112 bytes
+
+*ALL* of the locations may be left empty. Some of the locations may be
+written by child function.
+
+TOC POINTER is used to restore addressibility of globals, but may be
+restored independently.
+
+SAVED LR is used to restore the return address, but the return address
+link register may be preserved using another method or control transferred
+in a different manner.
+
+BACK CHAIN stores previous stack pointer to permit walking the stack frames,
+but stack may be allocated and deallocated without storing it.
+
+Decrementing the stack pointer by 112 bytes at the beginning of a function
+and incrementing the stack pointer by the complementary amount is sufficient
+to interact with other ABI-compliant functions.
+
"""
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